Actually balancing a rotating object at the speeds of interest in a drivetrain can drive the finished goods price up a lot. I suspect that the reason robust CV shafts can be purchased at low prices has to do with skimping on or foregoing the final balancing.
With a CV shaft, to balance it right you have to first balance the components (joint ends etc) separately, before assembly. Then once assembled you have to do the balance correction, making those corrections at the flange (if the CV shaft has one) and the parts rigidly attached to that flange.
CV shafts being fairly small, generally, many if not most manufacturers don’t even try to do that. ESPECIALLY the short shafts like the driver’s side front on the AWD/FWD volvos. Consequently, drivers that have the necessity, the opportunity or a flexible regard for speed limits soon find out that the better shafts are very well balanced and many (not all) of the aftermarket ones are.
You can kind of sort of divide the “market” into tiers:
OEM tier: Some OEs (cough cough Toyota) make, or have affiliated or high quality aftermarket suppliers (ahem, Ford makes some, has GKN make some, etc.) make, their CV axles.
High quality aftermarket (i.e.: GKN, NTN, Raxles, FEBI (Bilstein), and SKF, generally)
Mass quality aftermarket (i.e.: TrakMotive, GSP, DSS, SSL)
Economy aftermarket (pretty much everyone else)
The OEMs and high quality aftermarket suppliers tend to do mch better balancing of the CV axles than the economy aftermarket tier suppliers. The economy aftermarket tier takes advantage of a couple things. First: short CV axles, by definition, can’t be but so far out of balance and on cars the wheels generally rotate 381 to 1250 revolutions per mile depending on tire diameter (see Off Road Tires, Off Road Wheels & Accessories | National Tire & Wheel). At slower speeds, CV shaft imbalances aren’t really perceptible. Makers of inexpensive axles rely on that phenomenon. Buyers of all axles, expensive or not, can’t readily measure axle imbalance or even runout for that matter. And, balancing a CV axle costs time, which translates to money. In order to guarantee that every axle that goes out the door is nearly perfectly balanced you have to budget for balancing them all. The better they are before balancing the more profit you make, granted, but you have to allow for the resources for that balancing in your standard costs in order to get there.
With the challenge in balancing being to get the shafts balanced right before going out the door, if you think about it it’s logical to (correctly) conclude that the least expensive way to get a good replacement shafs is to rebuild your OE shaft(if it is not bent) or buy an OEM shaft from a junkyard and overhaul it.
There may be an “out” however. Three things:
- One – new shafts are not but so far off balance due to relatively tight manufacturing tolerances in order to make them marketable at all. If yo ureplace a wonky shaft, odds ae not bad that a new replacement will be better especially if you don’t cheap out in the first place.
- Two – you can balance a shaft yourself, empirically using (of all things) worm-gear hose clamps on the axle that you reposition until the vibrations minimize or disappear. However, while it’s technically possible to use worm gear clamps to balance a CV axle, it’s generally not recommended and certainly isn’t standard method. Balancing a CV axle usually involves adding or removing weight at specific locations on the axle to counteract imbalances, and this is best achieved with specialized balancing equipment and techniques. Using a worm gear, you are test driving the vehicle at speed, repeatedly until you get the balance right; you are in danger of having to position the clamp where it whacks things on rotation; and you may invite corrosion over time. That said, it is an old-school method involving raising the vehicle and using a piece of chalk to mark the heavy spot while the shaft rotates. Then, hose clamps are placed opposite the chalk mark and adjusted until the vibration is reduced or eliminated.
- Three – you can get dynamic axle dampers, actually. Toyota sells them, see this Toyota part search: https://toyotaparts.lakelandtoyota.com/search?search_str=Drive Shaft Damper&ptid=11638 – what youhave to do is find their damper (they are in various sizes) that will fit your axle. Remember, however, that the issues with these dampers, mainly rusting away of the axle underneath, are still a thing to be reckoned with.
Just some thoughts. Have not tried them yet.
Albertj